it should be enough, but why dont you buy like a 5770, should be pretty cheap used also , and only requires one pci-e connector, performs noticeably better, uses less power, has dx11
and if that is too much then the 5750 also performs on same level as the 9800gtx+ and also uses less power, and needs only 1 pci-e connector
also I am guessing you're buying used since the 9800gtx+ is an old card... or you have one lying around.. in that case ignore everything I said and use it lol